let emailArr = ['123456.a@abc.com', '123456a@abc.com', '123456+a@abc.com', '123456@abc.com']
function uniqEmail(arr) {
    let newArr = []
    for(let item of arr) {
        item = item.split('')
        if(item.indexOf('.') !== item.lastIndexOf('.')) {
            let key = item.indexOf('.')
            item.splice(key, 1)
        }
        if(item.includes('+')) {
            let key1 = item.indexOf('+')
            let key2 = item.indexOf('@')
            let num = key2 - key1
            item.splice(key1, num)
        }
        newArr.push(item.join(''))
    }
    return newArr
}
let res = uniqEmail(emailArr)
res = [...new Set(res)]
